ALK dropping on new system

[Aeb1419]

I started my tank in mid september. It is a reefer 250 with a refugium and sump so total gallons is about 75. I used IO salt as my beginning salt mix (plannin to change to reef crystals after I start running out) I cycled with no light for about a month. After that I did a water change ( 20%)and added my first livestock, 2 fish and one torch coral. I let things settle until next day and I read my parameters. (Using hanna nitrate, pH and phosphate readers with saliferts calk and alk test kits)

10/29 (1st reading added torch and two fish)
pH: 8.0
Alkalinity: 7.3
Nitrate: 29.4
Phosphate: 0.0
Salinity: 1.025
Calcium: 410

Everything has been looking great and chaeto is growing and no algae in my display (it almost looks too clean which kind of worries me) I was not planning to do a water change as my goal is to do monthly water changes.

Read parameters today and got the following:

11/4
pH: 8.4
Alkalinity: 6.4
Nitrate: 35.6
Phosphate: 0.05
Salinity: 1.026
Calcium: 410

I expected the nitrate and phosphate to go up with fish and more frequent feedings but was not expecting the sudden rise in pH and the drop in Alk. Not sure whats going on. Both readings of parameters were done in the morning about 9am. No lights are on at this time (this includes refugium and display lights) should I be concerned? Calcium is reading normal as before and I did the test twice for Alk just to make sure and got the same reading. Planning on increasing light intensity on the fuge as well as the photo period to keep NO3 and PO4 at bay. Any suggestions on what may be happening to pH and Alk?

 

[Randy Holmes-Farley]

Rising nitrate depletes alkalinity. The ammonia to nitrate conversion is what depletes alk.

I'd ignore the pH. It's fine, although it may also be test error. pH is never too high when not dosing high pH additives.

 

[Aeb1419]

Increasing fuge light intensity and photoperiod will help? Im guessing not since the ammonia conversion to nitrate will still happen.

 

[Randy Holmes-Farley]

Increasing fuge light intensity and photoperiod will help? Im guessing not since the ammonia conversion to nitrate will still happen.

If you consume more nitrate, that adds back alkalinity lost in the initial conversion.

 

[Aeb1419]

If you consume more nitrate, that adds back alkalinity lost in the initial conversion.

After doing this hobby for the past 6 years I thought I had everything down already but Im still learning everday. Thanks for your help

 

[Randy Holmes-Farley]

After doing this hobby for the past 6 years I thought I had everything down already but Im still learning everday. Thanks for your help

You’re welcome.

Happy Reefing!

 

[Ordovician_Reef]

If you consume more nitrate, that adds back alkalinity lost in the initial conversion.

First off, thank you for your expert help and advice. It is appreciated. Our 200 gallon is in a room with very good circulation so our pH varies from 8.25 to 8.5 through the course of the day. I drip Kalk, heavier at night and run a 10 gallon in sump refugium on a reverse photo period. Would you consider this variation to be acceptable?

Our Alk is pretty steady at 7.3 to 7.5 and calcium is at 420-460. I have room to dose more Kalk (evaporation is good) but am a little worried about pushing the pH or Ca higher. I was considering starting Na Bicarbonite in the ATO to boost Alk into the 8.9 range. What would your thoughts be on that? I assume I would have to adjust salinity in the long term to compensate for the Na accumulation. I am also considering AFR.

 

[Lavey29]

I started my tank in mid september. It is a reefer 250 with a refugium and sump so total gallons is about 75. I used IO salt as my beginning salt mix (plannin to change to reef crystals after I start running out) I cycled with no light for about a month. After that I did a water change ( 20%)and added my first livestock, 2 fish and one torch coral. I let things settle until next day and I read my parameters. (Using hanna nitrate, pH and phosphate readers with saliferts calk and alk test kits)

10/29 (1st reading added torch and two fish)
pH: 8.0
Alkalinity: 7.3
Nitrate: 29.4
Phosphate: 0.0
Salinity: 1.025
Calcium: 410

Everything has been looking great and chaeto is growing and no algae in my display (it almost looks too clean which kind of worries me) I was not planning to do a water change as my goal is to do monthly water changes.

Read parameters today and got the following:

11/4
pH: 8.4
Alkalinity: 6.4
Nitrate: 35.6
Phosphate: 0.05
Salinity: 1.026
Calcium: 410

I expected the nitrate and phosphate to go up with fish and more frequent feedings but was not expecting the sudden rise in pH and the drop in Alk. Not sure whats going on. Both readings of parameters were done in the morning about 9am. No lights are on at this time (this includes refugium and display lights) should I be concerned? Calcium is reading normal as before and I did the test twice for Alk just to make sure and got the same reading. Planning on increasing light intensity on the fuge as well as the photo period to keep NO3 and PO4 at bay. Any suggestions on what may be happening to pH and Alk?

I see you already received good info for your concern but I'm going to suggest you maintain weekly water changes the first year. New tanks will be unstable the majority of the first year with a variety of ugly phases and water changes aid in stability such as your alk fluctuations among other critical areas. After a year I transitioned to water changes every 3 weeks because my tank became much more stable and predictable.

 

[hexcolor reef]

I see you don’t have a reading for Magnesium, if you can check it you should